According to the iPhone dev team blog, the 3.0 OS firmware is jailbreakable on all devices. They have not yet issued a 3.0 jailbreak, but signs are promising for a release sooner than later. A jailbreak would open up the iPhone’s Unix chroot jail, allowing read-write access to the entire file system. Doing so on the iPhone lets users install BSD Unix tools, the Debian APT package management system, and OpenSSH.
Together, these tools provide a powerful suite for any iPhone developer, as they offer access to the same Unix tools as you’d find on a Mac. You can monitor your processes, look directly at the files in your sandbox (and edit them if necessary), and interact directly with the iPhone system. Many developers have built scripts and command line utilities that further enhance the iPhone-end of development.
As I’ve said before, I think Ars Technica spends way too much on jailbreaking and hacking iPhones, but this is an interesting argument – and one that might just hold water.